1. Field of the Invention
The present invention relates to a centrifugal clutch, in particular for motor vehicles.
2. Background Art
Clutches of this kind comprise a drum connected to a driven shaft and masses positioned free to move on a support disk connected to the drive shaft which, under the effect of the centrifugal force, transmit to the driven side of the clutch a given torque due to the contact force of a friction pad, mounted on the masses themselves, against the inner wall of the drum.
The masses are generally mounted by means of pins parallel to the axis of rotation of the disk, uniformly distanced on the disk itself.
When the disk is made to rotate, the masses rotate outwards under the effect of the centrifugal force, whilst the pads described a radial motion towards the inner wall of the drum, opposing a return force generally exerted by a helical screw. Beyond a certain rotating speed, the centrifugal force exceeds the aforesaid return force by a value equal to the force which the pads have to exert against the drum to transmit the rotation thereto.
In motor vehicles, and in particular in those designed for competitions, it is very important to determine the xe2x80x9cstallxe2x80x9d and xe2x80x9ccouplingxe2x80x9d rpm (revolution per minute) of the clutch.
Stall rpm is the number of revolutions of the engine in which, when the vehicle is stopped (brakes on), the torque transmitted by the clutch is in equilibrium with the one delivered by the engine.
Coupling rpm is the number of revolutions of the engine in correspondence with which the masses, expanding radially, start to come in contact with the inner wall of the drum.
There is also a transient from the start of the slipping when the masses actually connect with the wall of the drum until the number of revolutions of the clutch equals the number of revolutions of the engine.
The type of centrifugal clutch described above has some drawbacks.
In clutches of this kind, the stall and coupling speeds depend not only on the centrifugal masses, but also on the characteristics of the return spring. Therefore, if the stall and coupling speed are to be changed, normally it is opportune to change the return springs.
To make this change, it is necessary completely to disassemble the clutch, so as to replace the existing springs with springs having different elastic characteristics.
The aim of the present invention is to obtain an enhanced centrifugal clutch in which the stall and coupling regimes can easily be changed.
In accordance with an aspect of the present invention, a centrifugal clutch is presented as specified in claim 1.
The dependent claims refer to preferred and advantageous embodiments of the invention.